Re: [STLinux Kernel] [PATCH 4/8] serial: st-asc: (De)Register GPIOD and swap Pinctrl profiles

Peter Griffin
2017-01-25T11:24:59Z

Hi Lee,

On Tue, 24 Jan 2017, Lee Jones wrote:

> When hardware flow-control is disabled, manual toggling of the UART's
> reset line (RTS) using userland applications (e.g. stty) is not
> possible, since the ASC IP does not provide this functionality in the
> same was as some other IPs do. Thus, we have to do this manually.
>
> This patch ensures that when HW flow-control is disabled the RTS/CTS
> lines are free to be registered via the GPIO API. It also ensures
> any registered GPIO lines are unregistered when HW flow-control is
> requested, allowing the IP to control them automatically.

Apart from my comment in previous mail about switching the meaning of
default & manual-rts groupings. It seems like a neat solution.

Acked-by: Peter Griffin <peter.griffin@linaro.org>

>
> Signed-off-by: Lee Jones <lee.jones@linaro.org>
> ---
> drivers/tty/serial/st-asc.c | 27 ++++++++++++++++++++++++++-
> 1 file changed, 26 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/tty/serial/st-asc.c b/drivers/tty/serial/st-asc.c
> index 03801ed..2c4b5f5 100644
> --- a/drivers/tty/serial/st-asc.c
> +++ b/drivers/tty/serial/st-asc.c
> @@ -512,6 +512,8 @@ static void asc_set_termios(struct uart_port *port, struct ktermios *termios,
> struct ktermios *old)
> {
> struct asc_port *ascport = to_asc_port(port);
> + struct device_node *np = port->dev->of_node;
> + struct gpio_desc *gpiod;
> unsigned int baud;
> u32 ctrl_val;
> tcflag_t cflag;
> @@ -555,9 +557,32 @@ static void asc_set_termios(struct uart_port *port, struct ktermios *termios,
> ctrl_val |= ASC_CTL_PARITYODD;
>
> /* hardware flow control */
> - if ((cflag & CRTSCTS))
> + if ((cflag & CRTSCTS)) {
> ctrl_val |= ASC_CTL_CTSENABLE;
>
> + /* If flow-control selected, stop handling RTS manually */
> + if (ascport->rts) {
> + devm_gpiod_put(port->dev, ascport->rts);
> + ascport->rts = NULL;
> +
> + pinctrl_select_state(ascport->pinctrl,
> + ascport->states[DEFAULT]);
> + }
> + } else {
> + /* If flow-control disabled, it's safe to handle RTS manually */
> + if (!ascport->rts && ascport->states[MANUAL_RTS]) {
> + pinctrl_select_state(ascport->pinctrl,
> + ascport->states[MANUAL_RTS]);
> +
> + gpiod = devm_get_gpiod_from_child(port->dev, "rts",
> + &np->fwnode);
> + if (!IS_ERR(gpiod)) {
> + gpiod_direction_output(gpiod, 0);
> + ascport->rts = gpiod;
> + }
> + }
> + }
> +
> if ((baud < 19200) && !ascport->force_m1) {
> asc_out(port, ASC_BAUDRATE, (port->uartclk / (16 * baud)));
> } else {